Long-term variability of aerosol optical thickness in Eastern Europe over 2001–2014 according to the measurements at the Moscow MSU MO AERONET site with additional cloud and NO<sub>2</sub> correction

Abstract

Abstract. The aerosol properties of the atmosphere were obtained within the framework of the AERONET program at the Moscow State University Meteorological Observatory (Moscow MSU MO) over 2001–2014 period. The quality data control has revealed the necessity of their additional cloud and NO2 correction. The application of cloud correction according to hourly visual cloud observations provides a decrease in average aerosol optical thickness (AOT) at 500 nm of up to 0.03 compared with the standard dataset. We also show that the additional NO2 correction of the AERONET data is needed in large megalopolis, like Moscow, with 12 million residents and the NOx emission rates of about 100 kt yr−1. According to the developed method we estimated monthly mean NO2 content, which provides an additional decrease of 0.01 for AOT at 340 nm, and of about 0.015 – for AOT at 380 and 440 nm. The ratios of NO2 optical thickness to AOT at 380 and 440 nm are about 5–6 % in summer and reach 15–20 % in winter when both factors have similar effects on UV irradiance. Seasonal cycle of AOT at 500 nm is characterized by a noticeable summer and spring maxima, and minimum in winter conditions, changing from 0.08 in December and January up to 0.3 in August. The application of the additional cloud correction removes a local AOT maximum in February, and lowered the December artificial high AOT values. The pronounced negative AOT trends of about −1–5 % yr−1 have been obtained for most months, which could be attributed to the negative trends in emissions (E) of different aerosol precursors of about 116 Gg yr−2 in ESOx, 78 Gg yr−2 in ENMVOC, and 272 Gg yr−2 in ECO over European territory of Russia. No influence of natural factors on temporal AOT variations has been revealed.

Columnar and surface urban aerosol in the Moscow megacity according to measurements and simulations with the COSMO-ART model

“…However, AODs were slightly smaller compared with corresponding monthly average values over the 2001-2020 period. This is in agreement with the observed negative AOD trend in the Moscow megacity (Chubarova et al, 2016;Zhdanova et al, 2020). A reduction in the fine-mode AOD fraction may be associated with a decrease in the emissions of urban aerosol gas precursors in recent years (Zhdanova et al, 2020).…”

“…The summer AOD500 maximum is associated with the active formation of submicron aerosol with a fine-mode AOD500 fraction higher than 80 %. The April-May period of 2018-2019 is characterized by slightly lower AOD500, which is in agreement with a negative AOD500 trend in Moscow in recent years (Chubarova et al, 2016;Zhdanova et al, 2020). The lower fraction of fine-mode aerosol (64 % compared with 71 %-73 %) may also indicate the decrease in the formation of secondary aerosol due to the effective reduction of urban gas precursor emissions in Moscow (Zhdanova et al, 2020).…”

“…Its detailed testing revealed that the new algorithm of automatic cloud filtration, applied in this version, worked much better than the old one, with the exception of the winter months (Chubarova, 2020). As a result, we did not apply additional cloud filtering, as has been previously done (Chubarova et al, 2016). During daytime the dataset has 15 min resolution of the aerosol characteristics obtained from the direct sun measurements and 1 h resolution from sky measurements.…”

Multi-year analysis of aerosol optical properties at various timescales using AERONET data in tropical West Africa

“…This network was established by the National Aeronautics and Space Administration NASA and LOA-PHOTONS (CNRS) and has been expanded by collaborators at different levels (Holben et al, 1998). It is a well established data archive with over 400 stations worldwide (Chubarova, Poliukhov, & Gorlova, 2016) providing a database of aerosol optical, microphysical and radiative properties for the purpose of aerosols research and characterization. The data is validated against other data archives and the network is known for its standardization of instruments, calibration, processing and distribution (Holben et al, 1998;Smirnov, Eck, Dubovik, & Slutsker, 2000).…”

Detection of a gas flaring signature in the AERONET optical properties of aerosols at a tropical station in West Africa

“…AERONET network provides Sun photometer measurements of AOD at up to eight wavelengths between 340 and 1020 nm. The network has been in operation since mid-1990s [Holben et al, 1998] and currently with over Journal of Geophysical Research: Atmospheres 10.1002/2016JD025584 400 sites globally [Chubarova et al, 2016]. It also measures the angular distribution of sky radiance at four wavelengths (0.44, 0.67, 0.87, and 1.02 μm).…”